Ionized air cleaning device

ABSTRACT

METHOD AND APPARATUS FOR CLEANING A RESIDUAL TONER POWDER IMAGE BEARING SURFACE AFTER TRANSFER OF SUBSTANTIALLY ALL OF A CHARGED TONER IMAGE THEREFROM TO A SUPPORT MEDIUM. A FLOW OF IONIZED AIR IS DIRECTED TO THE SURFACE AND NEUTRALIZES ANY CHARGE ON THE RESIDUAL PARTICLES REMAINING ON THE SURFACE AFTER IMAGE TRANSFER TO ALLOW THE PARTICLES TO BE READILY REMOVED. A NOZZLE IS UTILIZED TO DIRECT THE FLOW AGAINST THE SURFACES AND IONIZES THE AIR FLOWING THERETHROUGH BY APPLYING A POTENTIAL BETWEEN TWO ELECTRICALLY INSULATED OPPOSITE SIDES OF THE NOZZLE.

cs. T. SEVERYNSE IONIZED AIR cwmme DEVICE June 6, 1972 Filed June 4,1969 2 Sheets-Sheet 1 ELECTRICAL POTENTIAL INVENTOR. GERARDT SEVERYNSE IATTORNEY j Jun 6, 1972 s. -r. SEVERYNSE 3,668,008

IONIZED Am CLEANING DEVICE Filed June 4, 1969 2 Sheets-Sheet 3 UnitedStates Patent 3,668,008 IONIZED AIR CLEANING DEVICE Gerard T. Severynse,Fairport, N.Y., assignor to Xerox Corporation, Rochester, NY. Filed June4, 1969, Ser. No. 830,337 Int. Cl. G03g 13/00, 15/00; B08!) 5/00 US. Cl.134-1 8 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTIONThis invention relates to a method and apparatus for cleaning residualtoner powder from an electroscopic toner powder image bearing surfaceand, in particular, to an improved method and apparatus for neutralizingthe charge on residual toner powder on a photoconductive insulatingsurface to facilitate easy removal of the particles.

More specifically, the invention relates to a cleaning method andapparatus adapted to clean residual toner powder images from aphotoreceptor wherein ionized air flows to the surface to be cleaned andneutralizes the particles thereon to allow the particles to be readilyremoved. Neutralization of the particles is effected by creating an airflow through a nozzle which ionizes the flow to form ions of positiveand negative polarities. The flow is directed onto the surface toneutralize the particles thereon. The nozzle ionizes the air byproducing a corona discharge between the two parallel walls of thenozzle thereby ionizing the air flowing therebetween. The air, afterpassing from the ionizing nozzle, impinges against the residualparticles on the surface to neutralize the charge on the particles andthe flow itself carries off the neutralized material. Alternatively, theionized flow may be directed against the surface to neutralize theparticles and the neutralized particles removed by another convenientremoval method such as a brush or vacuum nozzle.

Although not intended to be so limited, for convenience of illustrationthe cleaning device and method of this invention are described for usein an automatic xerographic reproducing machine. In the process ofxerography, a Xerographic plate comprising a layer of photoconductivematerial on a conductive backing is given an uniform electric chargeover its surface and is then exposed to the subject matter to bereproduced by various projection techniques. This exposure dischargesthe plate in accordance with the light intensity reaching it, thereby,creating a latent electrostatic image on or in the plate.

Development of the image is effected by developers which comprise, ingeneral, a mixture of suitable pigmented or dyed resin base powder,hereinafter referred to as toner, and a granular carrier material whichfunctions to generate triboelectric charges on and to carry the toner.More specifically, the function of the carrier material is to provide amechanical control of the toner or to carry the toner to an imagesurface and simultaneously provide almost complete homogeneity of chargepolarity.

3,668,008 Patented June 6, 1972 In the development of the image, thetoner powder is brought into surface contact with th photoconductivesurface and held there electrostatically in a pattern corresponding tothe latent electrostatic image. Thereafter, the developed toner powderimage may be transferred to a support material to which it may be fixedby any suitable means such as heat fusing.

In high speed xerographic equipment, the photoconductive plate is oftenin the form of a drum or belt which allows the surface to sequentiallypass through a plurality of xerographic processing stations. Such amoving photoconductive surface can thereupon be readily reused andanother duplication cycle effected. However, in practice, transfer ofthe toner image to the support material is incomplete leaving a residualtoner powder image on the photoreceptor surface. Such residual tonerimages are detrimental to the reuse of the surface and have an adverseeifect on reproductions produced in subsequent operations of thexerographic device. One cause of the incomplete transfer of the toner isthat toner generally comprises a range of sizes, and the largerparticles tend to readily transfer while the smaller particles are aptto remain attached to the photoconductor because of the electrostaticattraction of these charged particles to the charged plate. The smallerparticles are more difiicult to transfer to the support material, sincethey usually carry less electrostatic charge than larger toner particlesand,-

therefore, require a greater electric field for removal from thephotoreceptor than do the larger toner particles which result in lesseflicient transfer. The residual toner is electrostatically attached tothe photoconductor by the charge that exist on the surface of the tonerlayer as well as at the interface between the toner powder and thephotoreceptor surface. Generally, after transfer the residual tonerpowder has an electrical charge that varies in magnitude and evenpolarity depending on conditions, for example, such as relativehumidity, temperature, the transfer current used to effect transfer ofthe toner powder to the support material, paper moisture content, andthe composition of the developer material.

One known technique of removing residual images from a photoconductivesurface after transfer has been by the use of a rotating brush. Thebrush cleaner is generally made of a soft material which rotates againstthe residual toner powder bearing surface to remove the residualparticles. An example of such a cleaning system is disclosed in Walkupet al., US. Pat. 2,832,977, issued May 6, 1958 wherein a brush, havingan electrical charge applied to its bristles, contacts the particles andattracts them from the drum. A vacuum system is operatively connected tothe brush to remove the toner collected on the bristles to preventinefficient cleaning or abrasion of the photoreceptive surface resultingfrom the accumulation of toner on the brush bristles.

Several problems are associated with the brush tech nique of cleaningthe xerographic surface. One difficulty lies in the selection of thematerial of the brush itself since the brush must be soft enough not todamage or scratch the photoconductive surface and yet abrasive enough toremove the particles firmly fixed to the photoconductor by electrostaticattraction. Also, the brush material must be capable of retaining asufficient charge to attract the toner particles in the manner intended.However, even after a careful selection of the brush material, damagecan occur to the photoreceptor surface after repeated cleaning due tothe abrasion of the brush fibers contacting the surface to removeresidual toner firmly retained by electrostatic forces. Further,repeated cleaning causes the brush bristles to become weaken resultingin ineffective cleaning of the surface making it necessary to frequentlyreplace these components. Such changing of the brush is inconvenient anduneconomical in continued use of the xerographic equipment.

Another difliculty that arises in conjunction with brush cleaning is theaccumulation of toner powder on the brush which results in toner beingreapplied to the photoconductor surface as the brush becomes clogged.The accumulation requires the use of a vacuuming system to clean thebrush which increases the machine size and expense as well as beingineffective in maintaining a completely clean brush. Also, brushcleaners do not sufficient- 1y neutralize the charge on the tonerparticles even when the bristles are electrically biased andneutralization by a brush is particularly difficult when the tonercharge varies in magnitude and polarity.

One technique devised as an attempt to overcome some of the problemspresented by brush cleaning was the use of a web cleaner. An example ofa web cleaner is disclosed in Eichorn, US. Pat. No. 3,190,198, issuedJune 22, 1965, wherein a cleaning web is brought into rubbing contactwith a photoreceptor to remove the residual toner powder image. Inpractice, the web moves relative to the photoconductive layer at aslower speed then the photoreceptive surface and scrapes off theresidual toner. However, as is the case with the brushes, the web is infrictional contact with the drum and it becomes difiicult to applysufficient pressure to remove the particles and yet not abrade thephotoconductive layer. Further, the material used as a web must havesuch properties as to sufficiently clean the surface and yet again notto damage the photoreceptor. Often the web is coated with a tonercollecting substance which leaves a residual coating on the surface andis detrimental in further use of the photoreceptor. Another difiicultyof web cleaning is that a thin layer of toner can remain on thephotoreceptor since it is usually not possible to apply the necessarypressure for adequate cleaning of electrostatically adhering particles.Generally, the particles that are not removed are the smaller particleswhich are electrostatically bonded to the photoreceptor after imagetransfer. It has been attempted in the prior art to place a charge onthe cleaning web to facilitate removal of the toner throughneutralization of the charge on the particles, but even in such a systemthe problem of abrasion on the drum and insufiicient removal of thetoner powder film still remains because such a charged web has provenrelatively ineffective in neutralizing the varying magnitude andpolarity of the charged toner. It, therefore, becomes desirable toutilize a cleaning technique which overcomes many of the aforementionedproblems associated with prior art cleaning methods.

A copending appplication, Ser. No. 830,314, filed concurrently with thepresent application and entitled Surface Cleaning By Ionized Flow, byFrederick W. Hudson, discloses a method and apparatus which overcomesmany of the aforementioned problems presented by the prior art cleaningtechniques. The copending application accomplishes this improvedcleaning by directing a flow of air which has been ionized into negativeand positive charges by corona wires against a surface bearing residualimage particles to thereby neutralize the charge thereon and effectready removal of the particles from the surface. Even though thecopending application produces improved cleaning over prior art methods,it has been found that the technique utilizing corona wires to ionizethe flow suffers from the drawback of creating ions in the flow at alocation too remote from the surface. Thus, some of the positive andnegative ions formed in the flow have an opportunity to recombine tolessen the amount and number of charged ions reaching the surface to becleaned. Therefore, it is advantageous in ionized air flow cleaning tocreate the ionization of the air flow at a point as closely adjacent tothe residual particles as possible to insure that a greater amount ofcharge is carried to the photoreceptive surface.

4 SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto improve the cleaning of charged particles from a surface.

Another object of this invention is to improve the method and apparatusfor neutralizing residual toner powder images remaining on aphotoreceptor surface after trans fer of a toner image to a supportmember.

A further object of this invention is to improve the method andapparatus for ionizing air being impinged on a surface for the cleaningthereof.

These and other objects are attained in accordance with the presentinvention wherein there is provided a method apparatus for cleaningresidual electroscopic toner particles from a surface by utilizing aflow of ionized air to neutralize the charge on the particleselectrostatically affixed thereon. The air flow is created by any wellknown means such as a fan and is directed through a fluid conduit havinga nozzle at its end confronting the surface to be cleaned. The flow inthe method and apparatus of the present invention is ionized immediatelyadjacent the surface by utilizing the nozzle as an ion generator. Thenozzle is formed of two adjacent conductive surfaces electricallyinsulated from each other and having an electrical potential appliedbetween the two surfaces to create a corona discharge therebetween. Thecorona discharge ionizes the air flow passing through the nozzle intopositive and negative charges. By utilizing the nozzle as the iongenerator, recombination of the negative and positive charge iseliminated since the nozzle is in close proximity to the surface. Ashort transit time between ionization and contact with the residualparticles prevents this recombination. It has been found that the iongenerating nozzle of this invention greatly improves the neutralizationof charged residual particles, since a greater amount of ions impingesthereon because of the prevention of the recombination of the chargedparticles in the flow. Therefore, since the charge on the particles ismore effectively neutralized, the bond of the materials to the surfacebearing them is reduced to allow ready removal of the neutralizedparticles.

DESCRIPTION OF THE DRAWINGS Further objects of the invention togetherwith additional features contributing thereto and advantages accruingtherefrom will be apparent from the following description of severalembodiments of the invention when read in conjunction with theaccompanying drawings wherein:

FIG. 1 is a schematic illustration of a xerographic device utilizing thecleaning device of the present invention,

FIG. 2 is a frontal perspective illustration of one embodiment of thecleaning device of the present invention,

FIG. 3 is an enlarged perspective illustration of an embodiment of theionizing nozzle utilized in the cleaning device of FIG. 2 according tothe present invention; and,

FIG. 4 is an enlarged schematic illustration of a second embodiment ofionizing nozzle utilized in the cleaning device of FIG. 2.

FIG. 5 is an enlarged schematic illustration of still another embodimentof the ionizing nozzle utilized in the cleaning device of FIG. 2.

FIG. 6 is a schematic end view of the embodiment of the nozzleillustrated in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there isshown a schematic view of a drum type automatic Xerographic reproducingmachine utilizing the present invention. The central element of theapparatus is a drum 1 mounted for rotation and drivable in aconventional direction by a motor not shown. The drum 1 comprises anouter surface With a layer of photoconductive insulating material suchas vitreous selenium or other suitable surface. A uniform electrostaticcharge is placed on the photoconductive surface of the drum by means ofa conventional corona charging device 2. The uniformly charged surfaceon the drum is then moved to an exposure means 3 which may be any wellknown device which will expose the charged surface of copy to bereproduced, thereby, forming a latent electrostatic image of the copy onthe photoconductor drum surface in a manner well known in the art.

Following the formation of a latent electrostatic image of the copy tobe reproduced, the image on the drum will move to a development device 4to bring the charged image into contact with developer materialcomprising toner and carrier. The electric field of the charged imagecauses toner to aflix thereto and form a visible image. Afterdevelopment, the visible image moves to a transfer means 5 and istransferred from the drum to a web of paper 6 or other suitable supportmedium which is positioned in contact with the drum by rollers 7 and .8.A second corona charging device 9 applies a charge to the side of theweb opposite the image to facilitate transfer of the toner powder inimage configuration. The toner image on the web moves past the heatingelement 10 which permanently alfixes the toner to the paper web to forma duplicate of the original copy. A cleaning device 100 according to thepresent invention (to be hereinafter described in detail) contacts thephotoreceptor surface after it moves past the transfer device to removeany residual image material from the surface prior to a subsequentreproduction cycle. It should be clear that other modes of charging,exposing, transfer, and fusing may be utilized in connection with thepresent invention.

Referring now to FIG. 2, there is illustrated one embodiment of thecleaning device 100 according to the present invention. The cleaningdevice 100 includes a casing 21 which is mounted in brackets 22 to be inclose proximity to the drum surface and is of suflicient Width to extendacross the drum. The casing 21 forms a duct 23 wherein a flow of air iscreated by means of an air flow generating means 24 such as, forexample, a suitable fan. The flow of air created in the duct is directedonto the surface 1 bearing residual image and background material to beremoved. An adjustment member 25 is provided to allow the housing to berotatably moved so as to selectively adjust the angle that the flow ofair strikes the surface to be cleaned.

A nozzle 26 is mounted at the end of the duct directly adjacent thephotoconductor drum to increase the velocity of the air flow impingingon the surface and to ionize the air into positive and negative chargesfor neutralizing the charge on the residual image and backgroundparticles. The nozzle 26 extends the width of the drum to insure airflow striking all areas of the surface and includes two side walls 27and 28 of a conductive material which on their inner surfaces 29 and 30are in a parallel relationship to each other. The nozzle also includestwo end walls 31 and 32 on each side of the nozzle formed also of aconductive material wherein the end walls are separated from the twoparallel side walls by two strips 33 and 34 of insulating material onboth sides of the nozzle such as, for example, Teflon, to electricallyinsulate the two side walls from each other.

The electrically isolated side walls 27 and 28 of the nozzle (spacermembers 35 and 36 including electrically insulating materials) areconnected to an electrical potential to create a corona dischargebetween the two parallel surfaces 29 and 30 of the walls, The coronaemission created by the application of an electrical potential to thenozzle side walls results in ionization of the air flow into positiveand negative charges prior to the air flow reaching the surface to becleaned. The ionized air flow of both polarities thereupon impinges uponthe photoconductive surface and neutralizes any charge remaining on theelectroscopic toner after transfer of the image. It should be clear thatthe negative charges created in the ionized air will tend to neutralizethe positively charged particles and the positive charges in the flowwill tend to neutralize the negative charged particles. The enlargedperspective view of the nozzle 26 in FIG. 3 more clearly illustrates thestructure of the nozzle. It has been found that by utilizing the nozzlein the present'invention as the ionization means, the recombination ofpositive and negative charges which occurs rapidly in a flow of air isprevented, since the nozzle is in close vicinity of the photoconductorsurface. Therefore, the present invention greatly improves theneutralization of the charge on particles bonded to the surface to becleaned.

Referring now to FIG. 4, there is illustrated an embodiment of thenozzle which improves the corona breakdown of the air flowing betweenthe two parallel walls 29 and 30. The structure of FIG. 4 is identicalto that illustrated in FIG. 2 except that the knife edge 37 of thenozzle is formed with a series of serrations 38 shown, in FIG. 4, as aplurality of slots. The utilization of slots at the nozzle openings hasbeen found to greatly improve the corona breakdown between the surfacesthereby creating a significantly improved ionization of the air andprovide better neutralization of the charged particles lying on the drumsurface. The form of the serrations could be in other shapes and formssuch as a sawtooth pattern and the like, Also, the particular number ofserrations utilized depends on the desired degree of ionization of theair flow.

Referring now to FIGS. 5 and 6, there is illustrated another embodimentof the nozzle which improves the corona breakdown of the air flowingthrough the two parallel walls 29 and 30. Such an improved ionization ofthe air flowing through the nozzle is effected by a plurality of finetubes 39 extending along the direction of the flow of the air to form aseries of multiple jets. The plurality of tubes 39 are secured in anysuitable manner (not shown) within the flow passage of the nozzlecontained between the two end walls and the two side walls. The ends ofthe tubes extend from within the nozzles to slightly beyond the endthereof immediately adjacent the surface to be cleaned. Ionization ofthe air created in the form of this embodiment is produced by a seriesof corona wires 40 wherein a single corona wire is mounted in anysuitable means (not shown) to extend longitudinally within the tubemember and the corona wire is connected to a suitable bias potential.Therefore, the flow created by the fan is directed between the surfacesof the side and end walls of the nozzle and through the plurality oftubes to impinge upon the surface to be cleaned. Negative and positivecharges are created in the air flow through the tubes by means of thecorona wires ionizing the air. An insulating material 41 concentricallysurrounds each of the corona wires substantially the entire lengththereof except near the end adjacent the surface to be cleaned whereionization occurs because of corona emission. Therefore, it should beapparent that the flow of air is ionized by the plurality of tubes inthe immediate vicinity of the photoconductor surface. Since theembodiment of FIG. 5 ionizes the air by the passage of the plurality ofcorona wires, the necessity of a bias potential being connected to theparallel side walls as in the embodiments of FIGS. 3 and 4 0f the nozzleis obviously eliminated with the electrical bias for ionization in thisembodiment being applied between the conductive tubes 39 and thenoninsulated ends of the corona wires 40. Also, any number orarrangement of the thin tubes may be utilized-in the present inventiondepending on the desired degree of ionization of air.

The embodiments disclosed in this application effectively neutralize thecharge remaining on the particles of the surface to allow the particlesto be readily removed. The velocity of the flow of the ionized air canbe selected to physically remove neutralized particles to be carried toany suitable collection means such as a vacuum system or the like.Alternatively, the particles may remain on the surface afterneutralization by the flow of the ionized air according to the presentinvention,

and be physically removed from the surface by some convenient removaldevice such as a vaccum system, a lightly stroking brush, or the like.Therefore, the surface may be cleaned by the impact of the ionized flowstriking the surface to neutralize the charge on the particles thereonand to physically remove them from the surface, or the particles may beneutralized by the flow of ionized air and then removed by some otherconvenient method.

In the above description there has been disclosed an improved device andmethod for effectively cleaning a residual image from the xerographicphotoconductive surface after transfer of substantially all the image toa support material. The surface to be cleaned was described forconvenience of illustration as being that on a xerographic drum, but theinvention may be used to clean other wellaknown photoconductive membersin the form of plates, belts, webs or the like. It is further within thescope of the present invention to utilize the charged particleneutralizing and cleaning method and apparatus as described herein toremove charged particles from surfaces other than photoreceptors.

While the invention is described with reference to preferredembodiments, it will be understood by those skilled in the arts thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the true spirit and scope of theinvention. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its essential teachings.

What is claimed is:

1. Apparatus for removing electrically charged electroscopic particlesfrom a support member comprising duct means for coupling to an energysource for producing fluid flow,

a nozzle coupled to said duct means, said nozzle being mounted close toand extending over said support member, said nozzle having an exitorifice for directing fluid onto said support member to remove theparticles with impacting fluid,

said nozzle including at the exit orifice two electrically conductiveelectrodes electrically insulated from one another, said electrodesfacing each other forming a fluid conduit for passing fluid through thenozzle and said electrodes being arranged such that ions flow generallyparallel to said support member when an electrical energy source iscoupled to the electrodes, and

an electrical energy source coupled to said electrodes for ionizingfluid between them causing an ion flow generally parallel to saidsupport member to enable positive and negative ions to be diverted bythe fluid flow toward the support member.

2. The apparatus of claim 1 wherein said particles include tonerparticles and said support member comprises a photosensitive member onwhich latent electrostatic images are created and developed with saidtoner particles.

3. The apparatus of claim 1 wherein said electrodes include elongatedwalls generally parallel to one another 5. Apparatus for removingelectrically charged electroscopic particles from a support comprisingduct means for coupling to an energy source for producing fluid flow,

a nozzle coupled to said duct means supported close to and extendingover the support having an exit orifice for directing fluid onto thesupport to remove the particles with impacting fluid,

said nozzle including at the exit orifice spaced electrically conductivemembers electrically insulated from one another positioned within thepath of fluid flow, and

an electrical energy source coupled to said spaced members for ionizingfluid between them causing an ion flow generally perpendicular to thedirection of fluid flow to enable ions to be diverted by the fluid flowtoward the support, wherein said spaced electrically conductive membersinclude a plurality of conductive tubes each having a corona wirepositioned therein such that fluid flows through the tubes to thesupport and ionization occurs between a wire and the inner wall of atube.

6. A method of removing electrically charged electroscopic particlesfrom a support member comprising directing a flow of fluid through anozzle onto the support member to remove the particles with theimpacting fluid and applying an electrical potential between twoelectrodes electrically insulated from each other, the electrodes beingpositioned near the exit orifice of said nozzle, the electrodes forminga fluid conduit within said nozzle, the applying of the said electricalpotential ionizing fluid between the electrodes and generating an ionflow generally parallel to the support member, enabling positive andnegative ions to be diverted by the fluid flow toward the supportmember.

7. A method of removing electrically charged electroscopic particlesfrom a support comprising directing a flow of fluid through a nozzleonto the support to remove the particles with the impacting fluid andapplying an electrical potential between spaced members positioned nearthe exit orifice of said nozzle to ionize fluid between the membersgenerating an ion flow generally perpendicular to the fluid flowenabling ions to be diverted by the fluid flow toward the support,wherein said spaced members have edges that are serrated.

8. The method of claim 7 wherein said serrations are rectangular.

References Cited UNITED STATES PATENTS 1,169,428 1/1916 Rogers 317-2A1,678,869 7/1928 Morrison 317-2 A 1,940,536 12/1933 Eyler 317-2AX2,004,352 6/ 1935 Simon.

3,308,344 3/1967 Smith et a1 317-4 X 3,382,360 5/1968 Young et al.317-2X 3,396,308 8/1968 Whitmore 317-4 3,471,695 10/ 1969 Hudson et al.250-495 MORRIS O. WOLK, Primary Examiner D. G. MILLMAN, AssistantExaminer U.S. Cl. X.R.

